I was building a RORB model for a natural catchment that has parts that are hilly and other areas which are generally flat.
How does RORB differentiate between a catchment that has a higher average slope than another one that is flatter?
If two natural sub-catchments have the same area but one was hilly and one was flat, I would expect a higher rate of runoff from the hilly sub-catchment. But since RORB does not accept catchment slope as an input, would RORB think these are essentially the same when performing calculations?
RORB does take account of slope in some situations via the specification of reaches Have a look in the RORB manual section 2.2.3 and Table 2-2. Reach types 2 and 3 include slope as a parameter.
If you think that slope influences the relationship between storage and discharge for a particular catchment, then you could change the kc routing parameter.